Electrically driven timing device devoid of permanent magnet elements



Oct. 24, 1967 w U K 3,349,306

ELECTRICALLY DRIVEN TIMING DEVICE DEVOID OF PERMANENT MAGNET ELEMENTS Original Filed June 15, 1961 2 Sheets-Sheet 1 1 /& W ii A I '34} mumum 32%; i 24% C 26 7L INVENTOR. W L yI/PD E. Buck f76. 3. W, s bs ap m Oct. 24, 1967 w, BUCK 3,349,306

ELECTRICALLY DRIVEN TIMING DEVICE DEVOID OF PERMANENT MAGNET ELEMENTS Original Filed June 15, 1961 2 Sheets-Sheet 2 IN VEN TOR.

W/LL/l/PD E. BUCK o 2o 40 60 a0 /00 /20 1 y H6. Z ATTORNEYS United States Patent O 7 3,349,306 ELECTRICALLY DRIVEN TIMING DEVICE DE- VOID F PERMANENT MAGNET ELEMENTS Willard E. Buck, Boulder, Colo., assignor to Buck Instrument Co., Boulder, Colo., a corporation of Colorado Continuation of application Ser. No. 117,446, June 15, 1961. This application Mar. 25, 1966, Ser. No. 537,537 8 Claims. (Cl. 318128) This invention relates broadly to timing devices and more particularly to an electro-mechanical arrangement for use in driving such timing devices. This application is a continuation of application Ser. No. 117,446, filed June 15, 1961, now abandoned and contains subject matter in common with and constitutes a continuation-in-part of my co-pending application Ser. No. 512,696, now Patent No. 3,215,917, filed June 2, 1955, entitled, Electrically Driven Timing Device.

The primary object of the instant invention is to provide an improved electro-mechanical arrangement for driving a timing device which is both simple, durable and compact as well as accurate and of high efiiciency.

A further object of the present invention is to provide an improved electro-mechanical arrangement suitable for driving a timing device which avoids one or more of the disadvantages of prior art devices, and in which the accuracy is essentially independent of temperature.

A still further important object of the present invention is to provide an improved electro-mechanical arrangement suitable for driving a timing device which is characterized by long life, high reliability and is self starting. Other and further objects vwill be readily apparent as the description progresses and reference is had to the fol lowing description taken in connection with the accom panying drawings and its scope will be pointed out in the appended claims.

In the drawings: 7

FIGURE 1 is a schematic diagram in elevation illustrating a typical embodiment of the invention;

FIGURE 2 is a section taken along line 2-2 of FIG- URE l and looking down at the balance wheel;

FIGURE 3 illustrates a wiring diagram of another embodiment of the invention;

FIGURE 4 is a wiring diagram of still another embodi-. ment of the invention; a i

FIGURE 5 illustrates another embodiment of the invention;

FIGURE 6 is a section taken along line 6-6 of FIG- URE 5; and

FIGURE 7 is a graph illustrating certain electrical characteristics of semi-conductor devices useful in the instant invention.

Referring to the drawings and in particular to FIG- URES l and 2, there is shown a balance wheel 10 similar to those conventionally used in a watch and the like and is constructed of a suitable nonmagnetic material such as brass, for example. The balance wheel 10 is carried by a staff 12 which is supported at the ends in suitable bearings 14, 16. and provided with an adjustable hairspring 18. A disc 20 is provided carrying a roller pin 22 to cooperate with a suitable lever to provide an escapement. The spring 18 maintains the wheel 10 normally in a reference position and applies a force varying linearly with displacement from the reference position for returning the wheel to its reference position whenever it is displaced from same.

A magnetizable element 24 of ferromagnetic material having low residual induction, such as soft iron, is carried by a peripheral portion of wheel 10 which may conveniently be counterbalanced by a weight 26 positioned in diametrically opposed relation on the wheel periphery. A core 28 of magnetizable material of low residual in- 3,349,306 Patented Oct. 24, 1967 duction; and, has a pair of coils 30 and 32 wound thereon in the manner of an electromagnet. In FIGURE 1, the core is C-shaped and is positioned with respect to the balance wheel such that on oscillation thereof element 24 passes within the air gap between the pole pieces 27 and 29. Coils 30 and 32 are connected into a regenerative oscillator circuit comprising the coils, an amplifying device 34, such as a transistor and the like forming an am plifier and a source of power such as a battery 36. The coils are magnetically coupled and have mutual inductance from being wound around a single core. It will be appreciated that the mutual inductance can be accomplished in coils wound on separate cores which are coupled magnetically. One end of coil 30, as shown, is connected to the base '33 of transistor 34, while the other end is connected to the common juncture of resistor 38 and capacitor 40. The other end of resistor 38 is connected to the negative terminal of battery 36 or B- and the other end of capacitor is connected to the positive terminal of battery 36 or B+. Coil 32 has one end thereof connected to the emitter 39 of transistor 34 and the other end to B+. The collector 41 is connected to B.

The coupling and polarity of coils 30' and 32 are chosen such that the system will oscillate under proper bias conditions also when magnetizable element 24 is in position in the air gap between pole pieces 27 and 29 increasing the mutual inductance between coils 30 and 32. The circuit parameters and component values are chosen such that a single pulse of oscillation will charge condenser 40 sufficiently to effect a sufficient change in the bias to pre-. vent further oscillations in the system.

The appropriate bias for oscillation is restored by the discharge of the condenser 40 through resistor 38. Thus it will be seen that as element 24 enters the air. gap of core 28 there is an increase in the mutual inductance of the coils 30 and 32 sufficient to trigger the circuit into oscillation, however, the oscillation is limited to a single pulse due to the charging of condenser 40 which alters the bias on transistor 34. This pulse is reflected back into the core and attracts element 24 pulling this element further into the air gap imparting a power pulse to the wheel 10.

Once the single pulse is triggered by the entry of element 24 into the air gap further oscillations are prevented by thecharging of condenser 40 until the charge leaks off through resistor 38. The values of condenser 40 and resistor 38 are so chosen for a particular system to provide a time constant of. sufiicient magnitude to permit element 24 to travel to a point beyond the range where the ,coupling produced thereby is sufiicient to induce oscillation of the circuit yet sufiiciently short to permit the bias to be re-establis hed to the condition for the circuit to be triggered into. oscillation when element 24 re-enters the air gap on the return trip. As element 24 approaches and enters the gap from either direction, a pulseis generated in the circuit and a power or torque pulse is applied to theelement restoring .the velocity of the balance wheel. The power pulse occurs and is applied .very near the neutral point of spring 18, first on one side of the neutral point and then on the other. The application of the power pulse is close to the ideal to have the least effect on the accuracy of the time keeping of the balance wheel.

It will be readily appreciated that the electro-mechanrcal arrangement of the invention is adapted to be selfstarting because it is susceptible of being self-excited. An advantage which is-derived from the self-excitation characteristics of the system is that there is no permanent magnetic pull to add to the restoring force of the spring. If this restoring force were present it would be'temperature sensitive as the strength of a permanent magnet varies with changes in temperature. The absence of permanent magnets renders the system of this invention less sensitive to temperature changes and soft iron is more easily fabricated. With the component values chosen such that the presence of element 24 within the air gap will cause the circuit ,to oscillate, a power pulse is generated each time condenser 40 is charged. Repeated application of the power pulses forces element 24 against the restoring force of spring 18 causing the wheel to oscillate and build up to its natural period of oscillation. The oscillation is then maintained by the application of a power pulse to element 24 resulting from the oscillation pulse occasioned by element 24 entering the air gap. The different elements of construction are designed so that the power pulse given to element 24 and wheel 10 compensates for losses due .to friction and other possible losses as well as the mechanical energy expended by the escapement and an attached gear train, if any.

FIGURE 4 illustrates a circuit diagram similar to that of FIGURE 1 wherein coil 32 is connected to the collector 41 of transistor 34 instead of the emitter 39. The other end of coil 32 is connected to the negative terminal of battery 36 and to one end of resistor 38. One end of coil 30 is connected to base 33 of transistor 34 with the other end being connected to the other end of resistor 38 and one side of condenser 40, the other side of which is connected to the positive terminal of battery 36 along with the emitter 39. Coils 30 and 32 are both wound on core 28 which is positioned to act and to be acted upon by element 24 on wheel 10. This circuit operates much in the same fashion as that of FIGURE 1, wherein a power pulse is generated and applied to element 24, when this element is within the air gap of core 28. Here again the component values are chosen such that the increased coupling between coils 30 and 32 produces regeneration in the circuit and the charging of condenser 40 alters the bias on the transistor preventing more than a single pulse of oscillation to occur until the bias is restored by the charge on condenser 40 bleeding off through resistor 38. Each time element 24 enters the air gap, a power pulse is generated and applied thereto to maintain movement of the balance wheel.

The component values of the circuits of FIGURES 1 and 4 will vary largely with the characteristics of transistor 34. The graph in FIGURE 7 illustrates a plot of the resistance required against temperature for optimum results where condenser 40 is approximately 100 microfa-rads and a supply'voltage from about 6 to 12 volts DC. With some transistors resistor 38 will be required to be a high positive temperature coefficient resistor to correct for temperature change effects on the transistor. The 200T, 200TX and 903 transistors of FIGURE 7 are products of Texas'Instruments, .Inc., of Dallas, Tex., and the CK722 is a product of the Raytheon Company of Newton, Mass. It will be noted that a circuit utilizing a CK722 will operate satisfactorily over a rather wide temperature range of from approximately 20 F. to above 120 F. with resistor 38 having a value of approximately 50 ohms. By the use of resistors having a selected temperature coefiicient it is possible to incorporate a Wide variety of transistors in the proposed circuit design. 7

Referring to FIGURE 3, there is shown another embodiment of the circuit of the present invention wherein a unijunction semiconductor 42 is used. This device may be a 2N490 semiconductor'such as manufactured by the General Electric Company. This device is provided with three electrodes. One electrode 44 operates as a control electrode and functions to control the conducting of current between electrodes 44 and 48. The positive terminal of battery 36 is connected to electrode 46 of theunijunction semiconductor 42 and to one end of resistor 50. Resistor 50 is serially connected to resistor 52 and to the negative terminal of battery 36 forming a voltage dividing network. Electrode 48 of the unijunction semiconductor 42 is connected serially through coil 54 to the negative terminal of battery 36. Electrode 44 of unijunction semiconductor 42 is connected serially through resistor 56 to the common connection between resistors 50 and 52. A condenser 58 is connected between electrode 44 and the negative terminal of battery 36. The coil 54 is wound o core 28 leaving an air gap 29. Ferromagnetic element 24 of balance wheel 10 is positioned to move in and out of the air gap as mentioned with respect to FIGURE 1.

Component values for the circuit of FIGURE 3 using a 2N490 unijunction semiconductor which has a nominal resistance of fromabout 8K. to about 10K. between electrodes 46 and 48 may be reasonably varied. With a source voltage of from about 6 to 12 volts DC, the ratio of the resistance of resistor 50 to 52 is found to be about ap proximately 1 to 2-3, with values of 3K. and 7K. respectively being found satisfactory. The value of condenser may vary from about 2 to 7 microfarads and the value of resistor 56 may be from 25K. to K. depending upon the characteristics of the semiconductors. It will be appreciated that these values are only by way of example and should not be construed in any Way as limiting.

In operation, in the circuit of FIGURE 3, condenser 58 is charged up by battery 36 acting through voltage divider 50, 52 to. a potential just below that necessary to render the semiconductor conductive between elements 44 and 48. A small leakage current appears across elements 46 and 48 of the semiconductor and across coil 54. When the soft iron element 24 is within the air gap of core 28, the change in inductance of coil 54 is sufficient to render the semiconductor conducting whereupon condenser 58 discharges through coil 54 applying a power pulse to ele ment 24 and wheel 10. The component values of the circuit are chosen such that as element 24 enters the air gap, condenser 54 will be discharged and will be recharged by battery 36 as element 24 is returning for the next cycle.

Referring now to FIGURES 5 and 6, there is shown another embodiment of the invention wherein the coils 130 and 132 are physically separated but are coupled magnetically. The coils are wound on cores 128a and 12812 forming an integral part of a ferromagnetic plate 128 of soft iron. Plate 128 is formed with a generally circular shaped opening 134 joining slots to either side of cores 128a and 128b, which slots are of a size to receive coils 130 and 132. Cores 128a and 128b are positioned to either side of the opening 134 in plate 128 in approximately diametrically opposed relation. The ends of the cores 128a and 128k. adjacent the opening 134 are bent up as best seen in FIGURE 6 and secure the coils on the cores.

A balance Wheel is positioned within opening 134 of plate 128. Wheel 110 is carried by a staff 112 which is supported at the-ends in suitable bearings 114 and 116 and provided with an adjustable hairspring 118. A suitable escapement device is provided which, in this case, is shown as a ratchet wheel 120 and lever 122 for actuating a time recorder. Wheel 110 is provided with a pair of elements 124 and 126 on the pheriphery thereof. These elements and wheel 110 are ferromagnetic and may be integral with wheel 110 or secured thereto in suitable manner. Elements 124 and 126 are positioned normal to the plane of wheel 110 and lie closely adjacent to the upturned ends of cores 128a and 1281: respectively. Elements 124 and 126 are displaced by a small angle, normally five degrees or more, from being in perfect dimetrical opposition and cores 128a and 128k are positioned in like manner for the purpose to be presently explained.

Coils 130 and 132 are connected to circuitry such as shown in FIGURES land 4 and respectively occupy the positions-of coils 3.0 and 32 therein. The circuit operates in much the same manner. The polarity of the coils is such thatthe system will oscillate under proper bias conditions and when the soft iron pieces 124 and 126 of Wheel 110 are positioned to increase the mutual inductance of the coils.

Again the circuit component 'values are chosen such that a single pulse of oscillation charges up the condenser and alters the bias sufliciently to prevent further oscillation until the bias is restored by bleeding off the charge through the resistor. Thus as element 126 approaches adjacency with pole 12817 in a counterclockwise direction, the increased mutual inductance between coils 130 and 132 is enough to trigger a single pulse of oscillation which produces a pulse in coil 130 Whose phase is such as to transmit a power pulse to element 134 through pole 128a to continue the counterclockwise movement thereof against the restoring force of spring 118. Elements 124 and 126 are disposed at other than 180 degrees from each other in order to obtain a total rotational movement of the wheel of more than 180' degrees. The pulse of oscillation will only be generated when elements 124 and 126 are each adjacent poles 128a and 1281) respectively. It

will be appreciated that if the elements and poles were disposed in a 180 degree relationship, a power pulse would be generated on excursion of wheel 110 through 180 degrees. It is generally preferred that the rotary oscillation of the balance wheel be at least 200 degrees for accurate timing. It will be further appreciated by those skilled in the art that this desired result could similarly be obtained by proper circuit design; however, the mechanical solution is less complicated and more economical of execution.

While there have been described what at present are considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein,

without departing from the invention. It is aimed, therefore, in the appended claims to cover all such changes and modifications which fall within the true spirit and scope of the invention.

What is claimed is:

1. An electro-mechanical arrangement for driving a timing device comprising an oscillatable balance wheel carrying a ferro-magnetic member of low residual induction for rotation therewith, at least one ferro-magnetic core means having low residual induction with an air gap means positioned in the rotational paths of the ferromagnetic member of the balance wheel with said ferro magnetic member being positioned to pass into and completely out of said air gap on each oscillation of the balance wheel, at least one coil means mounted on said core and circuit means connected to said coil which circuit means when the ferro-magnetic member is Within the air gap of the core develops a current pulse through the coil and generates an electro-magnetic pulse which acts on said ferro-magnetic member to initiate and sustain the oscillation of the balance wheel, said device being devoid of permanent magnet elements.

2. The arrangement of claim 1 wherein the circuit means includes oscillator means adapted to generate a single pulse of oscillation when the ferro-magnetic member is in the air gap of the core.

3. An electro-mechanical arrangement for driving a timing device comprising an oscillatable balance Wheel carrying a ferro-magnetic member of low residual induction for rotation therewith, at least one ferro-magnetic core means having low residual induction with an air gap means positioned in the rotational paths of the ferro-magnetic member of the balance wheel, at least one coil means mounted on said core and circuit means connected to said coil which circuit means when the ferro-magnetic member is within the air gap of the core develops a current pulse through the coil and generates an electro-rnagnetic pulse which acts on said ferro-magnetic member to initiate and sustain the oscillation of the balance Wheel, wherein the circuit means includes an amplifier, a pair of coils mounted on a core, said coils being magnetically coupled with one coil being connected to supply a signal to the amplifier and the other connected to receive a signal therefrom on increasing the mutual inductance of the coils due to the presence of the ferro-magnetic member within the air gap and means responsive to the signal from said amplifier to alter the bias thereon to prevent further signals from being transmitted thereby while the ferromagnetic member is within the air gap.

4. An electro-mechanical arrangement for driving a timing device comprising an oscillatable balance wheel carrying a terror-magnetic member of low residual induction for rotation therewith, at least one ferro-magnetic core means having low residual induction with an air gap means positioned in the rotational paths of the ferromagnetic member of the balance wheel, at least one coil means mounted on said core and circuit means connected to said coil which circuit means when the ferro-magnetic member is within the air gap of the core develops a current pulse through the coil and generates an electromagnetic pulse which acts on said ferro-magnetic member to initiate and sustain the oscillation of the balance wheel, wherein the circuit includes an electronic switch means, storage means connected to the switch means to store an electric charge from an electric source, said electronic switch means being adapted to provide a discharge path from said storage means through the coil when the ferromagnetic member is within the air gap.

5. An electro-mechanical arrangement for driving a timing device comprising an oscillatable balance wheel carrying a retro-magnetic member of low residual induction for rotation therewith, at least one ferro-magnetic core means having low residual induction with an air gap means positioned in the rotational paths of the ferro-magnetic member of the balance wheel, at least one coil means mounted on said core and circuit means connected to said coil which circuit means when the ferro-magnetic member is within the air gap of the core develops a current pulse through the coil and generates an electro-magnetic pulse which acts on said ferro-magnetic member to initiate and sustain the oscillation of the balance wheel, wherein the circuit means includes an amplifier and said coil means comprises a pair of coils magnetically coupled, said coils being so connected to said amplifier and the amplifier being so biased to provide self-regeneration thereof on increase of the mutual inductance of the coils as by the presence of the ferro-magnetic member Within the air gap and means responsive to a single pulse of oscillation of said amplifier to bias same to a stable condition and prevent further oscillation thereof for a predetermined time interval.

6. An electro-mechanical arrangement for driving a timing device comprising an oscillatable balance wheel carrying a ferro-magnetic member of low residual induction for rotation therewith, at least one ferro-magnetic core means having low residual induction with an air gap means positioned in the rotational paths of the ferromagnetic member of the balance wheel, at least one coil means mounted on said core and circuit means connected to said coil which circuit means when the ferromagnetic member is within the air gap of the core develops a current pulse through the coil and generates an electro-magnetic pulse which acts on said ferro-magnetic member to initiate and sustain the oscillation of the balance wheel, wherein the circuit means includes an amplifier means having three electrodes, the first and second of which electrodes are connected across a source of electrical energy with the second electrode being connected serially through said coil and the third electrode is connected to the electrical source through a voltage divider network, capacitor means connected between said third electrode and the electrical source to receive and store a charge therefrom less than that required to render the amplifier means conductive between the third electrode and the second electrode, said amplifier means having a leakage path between said first and second electrodes to provide a leakage current across said coil and the presence of the ferro-magnetic member within the air gap means so alters the inductance of the coil as to render the amplifier means conducting between the second and third electrodes to discharge the condenser means therethrough and said coil generating an electromagnetic pulse which acts on said ferro-magnetic member to initiate and sustain the oscillation of the balance Wheel.

7. An electro-mechanical arrangement for driving a timing device which comprises a timing means including a balance wheel mounted for rotary oscillation having at least one magnetic member of low residual induction supported thereon, control means including electro-magnetic means operatively coupled to said timing means adapted to develop a timing pulse on oscillation of said timing means, drive means actuated by said timing pulse to sustain the oscillations of said timing means, means for applying said timing pulse to said drive means, wherein said control means and said drive means comprise an electromagnet having pole pieces of low residual induction with air gap means mounted with respect to the timing means such that a magnetic member passes through the air gap between the pole pieces as the timing means oscillates, said electromagnet having mounted thereon a .control coil control coil to said driving coil.

- 8. The arrangement of claim 7 wherein the means for electrically coupling the control coil to the driving coil includes an amplifier means having the control coil coupled to the input thereof and having the output thereof coupled to the driving coil.

References Cited MILTON O. HIRSHFIELD, Primary Examiner.

'D. F. DUGGAN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,349,306 October 24, 1967 Willard E. Buck It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, lines 4 and 5, for "Willard E. Buck, Boulder, Colo., assignor to Buck Instrument Co. Boulder, Colo. a corporation of Colorado" read Willard E. Buck, Boulder, Colo. 80302 Signed and sealed this 15th day of July 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents 

3. AN ELECTRO-MECHANICAL ARRANGEMENT FOR DRIVING A TIMING DEVICE COMPRISING AN OSCILLATABLE BALANCE WHEEL CARRYING A FERRO-MAGNETIC MEMBER OF LOW RESIDUAL INDUCTION FOR ROTATION THEREWITH, AT LEAST ONE FERRO-MAGNETIC CORE MEANS HAVING LOW RESIDUAL INDUCTION WITH AN AIR GAP MEANS POSITIONED IN THE ROTATIONAL PATHS OF THE FERRO-MAGNETIC MEMBER OF THE BALANCE WHEEL, AT LEAST ONE COIL MEANS MOUNTED ON SAID CORE AND CIRCUIT MEANS CONNECTED TO SAID COIL WHICH CIRCUIT MEANS WHEN THE FERRO-MAGNETIC MEMBER IS WITHIN THE AIR GAP OF THE CORE DEVELOPS A CURRENT PULSE THROUGH THE COIL AND GENERATES AN ELECTRO-MAGNETIC PULSE WHICH ACTS ON SAID FERRO-MAGNETIC MEMBER TO INITIATE AND SUSTAIN THE OSCILLATION OF THE BALANCE WHEEL, WHEREIN THE CIRCUIT MEANS INCLUDES AN AMPLIFIER, A PAIR OF COILS MOUNTED ON A CORE, SAID COILS BEING MAGNETICALLY COUPLED WITH ONE COIL BEING CONNECTED TO SUPPLY A SIGNAL TO THE AMPLIFIER AND THE OTHER CONNECTED TO RECEIVE A SIGNAL THEREFROM ON INCREASING THE MUTUAL INDUCTANCE OF THE COILS DUE TO THE PRESENCE OF THE FERRO-MAGNETIC MEMBER WITHIN THE AIR GAP AND MEANS RESPONSIVE TO THE SIGNAL FROM SAID AMPLIFIER TO ALTER THE BIAS THEREON TO PREVENT FURTHER SIGNALS FROM BEING TRANSMITTED THEREBY WHILE THE FERROMAGNETIC MEMBER IS WITHIN THE AIR GAP. 